<!DOCTYPE HTML>
< html lang = "zh-CN" class = "light sidebar-visible" dir = "ltr" >
< head >
<!-- Book generated using mdBook -->
< meta charset = "UTF-8" >
< title > 自定义 tracing 的输出格式 - Rust语言圣经(Rust Course)< / title >
<!-- Custom HTML head -->
< meta name = "description" content = "" >
< meta name = "viewport" content = "width=device-width, initial-scale=1" >
< meta name = "theme-color" content = "#ffffff" >
< link rel = "icon" href = "../favicon-de23e50b.svg" >
< link rel = "shortcut icon" href = "../favicon-8114d1fc.png" >
< link rel = "stylesheet" href = "../css/variables-8adf115d.css" >
< link rel = "stylesheet" href = "../css/general-2459343d.css" >
< link rel = "stylesheet" href = "../css/chrome-ae938929.css" >
< link rel = "stylesheet" href = "../css/print-9e4910d8.css" media = "print" >
<!-- Fonts -->
< link rel = "stylesheet" href = "../fonts/fonts-9644e21d.css" >
<!-- Highlight.js Stylesheets -->
< link rel = "stylesheet" id = "mdbook-highlight-css" href = "../highlight-493f70e1.css" >
< link rel = "stylesheet" id = "mdbook-tomorrow-night-css" href = "../tomorrow-night-4c0ae647.css" >
< link rel = "stylesheet" id = "mdbook-ayu-highlight-css" href = "../ayu-highlight-3fdfc3ac.css" >
<!-- Custom theme stylesheets -->
< link rel = "stylesheet" href = "../theme/style-78591068.css" >
<!-- Provide site root and default themes to javascript -->
< script >
const path_to_root = "../";
const default_light_theme = "light";
const default_dark_theme = "navy";
window.path_to_searchindex_js = "../searchindex-4dbab867.js";
< / script >
<!-- Start loading toc.js asap -->
< script src = "../toc-42887675.js" > < / script >
< / head >
< body >
< div id = "mdbook-help-container" >
< div id = "mdbook-help-popup" >
< h2 class = "mdbook-help-title" > Keyboard shortcuts< / h2 >
< div >
< p > Press < kbd > ←< / kbd > or < kbd > →< / kbd > to navigate between chapters< / p >
< p > Press < kbd > S< / kbd > or < kbd > /< / kbd > to search in the book< / p >
< p > Press < kbd > ?< / kbd > to show this help< / p >
< p > Press < kbd > Esc< / kbd > to hide this help< / p >
< / div >
< / div >
< / div >
< div id = "mdbook-body-container" >
<!-- Work around some values being stored in localStorage wrapped in quotes -->
< script >
try {
let theme = localStorage.getItem('mdbook-theme');
let sidebar = localStorage.getItem('mdbook-sidebar');
if (theme.startsWith('"') & & theme.endsWith('"')) {
localStorage.setItem('mdbook-theme', theme.slice(1, theme.length - 1));
}
if (sidebar.startsWith('"') & & sidebar.endsWith('"')) {
localStorage.setItem('mdbook-sidebar', sidebar.slice(1, sidebar.length - 1));
}
} catch (e) { }
< / script >
<!-- Set the theme before any content is loaded, prevents flash -->
< script >
const default_theme = window.matchMedia("(prefers-color-scheme: dark)").matches ? default_dark_theme : default_light_theme;
let theme;
try { theme = localStorage.getItem('mdbook-theme'); } catch(e) { }
if (theme === null || theme === undefined) { theme = default_theme; }
const html = document.documentElement;
html.classList.remove('light')
html.classList.add(theme);
html.classList.add("js");
< / script >
< input type = "checkbox" id = "mdbook-sidebar-toggle-anchor" class = "hidden" >
<!-- Hide / unhide sidebar before it is displayed -->
< script >
let sidebar = null;
const sidebar_toggle = document.getElementById("mdbook-sidebar-toggle-anchor");
if (document.body.clientWidth >= 1080) {
try { sidebar = localStorage.getItem('mdbook-sidebar'); } catch(e) { }
sidebar = sidebar || 'visible';
} else {
sidebar = 'hidden';
sidebar_toggle.checked = false;
}
if (sidebar === 'visible') {
sidebar_toggle.checked = true;
} else {
html.classList.remove('sidebar-visible');
}
< / script >
< nav id = "mdbook-sidebar" class = "sidebar" aria-label = "Table of contents" >
<!-- populated by js -->
< mdbook-sidebar-scrollbox class = "sidebar-scrollbox" > < / mdbook-sidebar-scrollbox >
< noscript >
< iframe class = "sidebar-iframe-outer" src = "../toc.html" > < / iframe >
< / noscript >
< div id = "mdbook-sidebar-resize-handle" class = "sidebar-resize-handle" >
< div class = "sidebar-resize-indicator" > < / div >
< / div >
< / nav >
< div id = "mdbook-page-wrapper" class = "page-wrapper" >
< div class = "page" >
< div id = "mdbook-menu-bar-hover-placeholder" > < / div >
< div id = "mdbook-menu-bar" class = "menu-bar sticky" >
< div class = "left-buttons" >
< label id = "mdbook-sidebar-toggle" class = "icon-button" for = "mdbook-sidebar-toggle-anchor" title = "Toggle Table of Contents" aria-label = "Toggle Table of Contents" aria-controls = "mdbook-sidebar" >
< span class = fa-svg > < svg xmlns = "http://www.w3.org/2000/svg" viewBox = "0 0 448 512" > <!-- ! Font Awesome Free 6.2.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2022 Fonticons, Inc. --> < path d = "M0 96C0 78.3 14.3 64 32 64H416c17.7 0 32 14.3 32 32s-14.3 32-32 32H32C14.3 128 0 113.7 0 96zM0 256c0-17.7 14.3-32 32-32H416c17.7 0 32 14.3 32 32s-14.3 32-32 32H32c-17.7 0-32-14.3-32-32zM448 416c0 17.7-14.3 32-32 32H32c-17.7 0-32-14.3-32-32s14.3-32 32-32H416c17.7 0 32 14.3 32 32z" / > < / svg > < / span >
< / label >
< button id = "mdbook-theme-toggle" class = "icon-button" type = "button" title = "Change theme" aria-label = "Change theme" aria-haspopup = "true" aria-expanded = "false" aria-controls = "mdbook-theme-list" >
< span class = fa-svg > < svg xmlns = "http://www.w3.org/2000/svg" viewBox = "0 0 576 512" > <!-- ! Font Awesome Free 6.2.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2022 Fonticons, Inc. --> < path d = "M371.3 367.1c27.3-3.9 51.9-19.4 67.2-42.9L600.2 74.1c12.6-19.5 9.4-45.3-7.6-61.2S549.7-4.4 531.1 9.6L294.4 187.2c-24 18-38.2 46.1-38.4 76.1L371.3 367.1zm-19.6 25.4l-116-104.4C175.9 290.3 128 339.6 128 400c0 3.9 .2 7.8 .6 11.6c1.8 17.5-10.2 36.4-27.8 36.4H96c-17.7 0-32 14.3-32 32s14.3 32 32 32H240c61.9 0 112-50.1 112-112c0-2.5-.1-5-.2-7.5z" / > < / svg > < / span >
< / button >
< ul id = "mdbook-theme-list" class = "theme-popup" aria-label = "Themes" role = "menu" >
< li role = "none" > < button role = "menuitem" class = "theme" id = "mdbook-theme-default_theme" > Auto< / button > < / li >
< li role = "none" > < button role = "menuitem" class = "theme" id = "mdbook-theme-light" > Light< / button > < / li >
< li role = "none" > < button role = "menuitem" class = "theme" id = "mdbook-theme-rust" > Rust< / button > < / li >
< li role = "none" > < button role = "menuitem" class = "theme" id = "mdbook-theme-coal" > Coal< / button > < / li >
< li role = "none" > < button role = "menuitem" class = "theme" id = "mdbook-theme-navy" > Navy< / button > < / li >
< li role = "none" > < button role = "menuitem" class = "theme" id = "mdbook-theme-ayu" > Ayu< / button > < / li >
< / ul >
< button id = "mdbook-search-toggle" class = "icon-button" type = "button" title = "Search (`/`)" aria-label = "Toggle Searchbar" aria-expanded = "false" aria-keyshortcuts = "/ s" aria-controls = "mdbook-searchbar" >
< span class = fa-svg > < svg xmlns = "http://www.w3.org/2000/svg" viewBox = "0 0 512 512" > <!-- ! Font Awesome Free 6.2.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2022 Fonticons, Inc. --> < path d = "M416 208c0 45.9-14.9 88.3-40 122.7L502.6 457.4c12.5 12.5 12.5 32.8 0 45.3s-32.8 12.5-45.3 0L330.7 376c-34.4 25.2-76.8 40-122.7 40C93.1 416 0 322.9 0 208S93.1 0 208 0S416 93.1 416 208zM208 352c79.5 0 144-64.5 144-144s-64.5-144-144-144S64 128.5 64 208s64.5 144 144 144z" / > < / svg > < / span >
< / button >
< / div >
< h1 class = "menu-title" > Rust语言圣经(Rust Course)< / h1 >
< div class = "right-buttons" >
< a href = "../print.html" title = "Print this book" aria-label = "Print this book" >
< span class = fa-svg id = "print-button" > < svg xmlns = "http://www.w3.org/2000/svg" viewBox = "0 0 512 512" > <!-- ! Font Awesome Free 6.2.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2022 Fonticons, Inc. --> < path d = "M128 0C92.7 0 64 28.7 64 64v96h64V64H354.7L384 93.3V160h64V93.3c0-17-6.7-33.3-18.7-45.3L400 18.7C388 6.7 371.7 0 354.7 0H128zM384 352v32 64H128V384 368 352H384zm64 32h32c17.7 0 32-14.3 32-32V256c0-35.3-28.7-64-64-64H64c-35.3 0-64 28.7-64 64v96c0 17.7 14.3 32 32 32H64v64c0 35.3 28.7 64 64 64H384c35.3 0 64-28.7 64-64V384zm-16-88c-13.3 0-24-10.7-24-24s10.7-24 24-24s24 10.7 24 24s-10.7 24-24 24z" / > < / svg > < / span >
< / a >
< a href = "https://github.com/sunface/rust-course" title = "Git repository" aria-label = "Git repository" >
< span class = fa-svg > < svg xmlns = "http://www.w3.org/2000/svg" viewBox = "0 0 496 512" > <!-- ! Font Awesome Free 6.2.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2022 Fonticons, Inc. --> < path d = "M165.9 397.4c0 2-2.3 3.6-5.2 3.6-3.3.3-5.6-1.3-5.6-3.6 0-2 2.3-3.6 5.2-3.6 3-.3 5.6 1.3 5.6 3.6zm-31.1-4.5c-.7 2 1.3 4.3 4.3 4.9 2.6 1 5.6 0 6.2-2s-1.3-4.3-4.3-5.2c-2.6-.7-5.5.3-6.2 2.3zm44.2-1.7c-2.9.7-4.9 2.6-4.6 4.9.3 2 2.9 3.3 5.9 2.6 2.9-.7 4.9-2.6 4.6-4.6-.3-1.9-3-3.2-5.9-2.9zM244.8 8C106.1 8 0 113.3 0 252c0 110.9 69.8 205.8 169.5 239.2 12.8 2.3 17.3-5.6 17.3-12.1 0-6.2-.3-40.4-.3-61.4 0 0-70 15-84.7-29.8 0 0-11.4-29.1-27.8-36.6 0 0-22.9-15.7 1.6-15.4 0 0 24.9 2 38.6 25.8 21.9 38.6 58.6 27.5 72.9 20.9 2.3-16 8.8-27.1 16-33.7-55.9-6.2-112.3-14.3-112.3-110.5 0-27.5 7.6-41.3 23.6-58.9-2.6-6.5-11.1-33.3 2.6-67.9 20.9-6.5 69 27 69 27 20-5.6 41.5-8.5 62.8-8.5s42.8 2.9 62.8 8.5c0 0 48.1-33.6 69-27 13.7 34.7 5.2 61.4 2.6 67.9 16 17.7 25.8 31.5 25.8 58.9 0 96.5-58.9 104.2-114.8 110.5 9.2 7.9 17 22.9 17 46.4 0 33.7-.3 75.4-.3 83.6 0 6.5 4.6 14.4 17.3 12.1C428.2 457.8 496 362.9 496 252 496 113.3 383.5 8 244.8 8zM97.2 352.9c-1.3 1-1 3.3.7 5.2 1.6 1.6 3.9 2.3 5.2 1 1.3-1 1-3.3-.7-5.2-1.6-1.6-3.9-2.3-5.2-1zm-10.8-8.1c-.7 1.3.3 2.9 2.3 3.9 1.6 1 3.6.7 4.3-.7.7-1.3-.3-2.9-2.3-3.9-2-.6-3.6-.3-4.3.7zm32.4 35.6c-1.6 1.3-1 4.3 1.3 6.2 2.3 2.3 5.2 2.6 6.5 1 1.3-1.3.7-4.3-1.3-6.2-2.2-2.3-5.2-2.6-6.5-1zm-11.4-14.7c-1.6 1-1.6 3.6 0 5.9 1.6 2.3 4.3 3.3 5.6 2.3 1.6-1.3 1.6-3.9 0-6.2-1.4-2.3-4-3.3-5.6-2z" / > < / svg > < / span >
< / a >
< a href = "https://github.com/sunface/rust-course/edit/main/src/logs/tracing-logger.md" title = "Suggest an edit" aria-label = "Suggest an edit" rel = "edit" >
< span class = fa-svg id = "git-edit-button" > < svg xmlns = "http://www.w3.org/2000/svg" viewBox = "0 0 512 512" > <!-- ! Font Awesome Free 6.2.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2022 Fonticons, Inc. --> < path d = "M421.7 220.3l-11.3 11.3-22.6 22.6-205 205c-6.6 6.6-14.8 11.5-23.8 14.1L30.8 511c-8.4 2.5-17.5 .2-23.7-6.1S-1.5 489.7 1 481.2L38.7 353.1c2.6-9 7.5-17.2 14.1-23.8l205-205 22.6-22.6 11.3-11.3 33.9 33.9 62.1 62.1 33.9 33.9zM96 353.9l-9.3 9.3c-.9 .9-1.6 2.1-2 3.4l-25.3 86 86-25.3c1.3-.4 2.5-1.1 3.4-2l9.3-9.3H112c-8.8 0-16-7.2-16-16V353.9zM453.3 19.3l39.4 39.4c25 25 25 65.5 0 90.5l-14.5 14.5-22.6 22.6-11.3 11.3-33.9-33.9-62.1-62.1L314.3 67.7l11.3-11.3 22.6-22.6 14.5-14.5c25-25 65.5-25 90.5 0z" / > < / svg > < / span >
< / a >
< / div >
< / div >
< div id = "mdbook-search-wrapper" class = "hidden" >
< form id = "mdbook-searchbar-outer" class = "searchbar-outer" >
< div class = "search-wrapper" >
< input type = "search" id = "mdbook-searchbar" name = "searchbar" placeholder = "Search this book ..." aria-controls = "mdbook-searchresults-outer" aria-describedby = "searchresults-header" >
< div class = "spinner-wrapper" >
< span class = fa-svg id = "fa-spin" > < svg xmlns = "http://www.w3.org/2000/svg" viewBox = "0 0 512 512" > <!-- ! Font Awesome Free 6.2.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2022 Fonticons, Inc. --> < path d = "M304 48c0-26.5-21.5-48-48-48s-48 21.5-48 48s21.5 48 48 48s48-21.5 48-48zm0 416c0-26.5-21.5-48-48-48s-48 21.5-48 48s21.5 48 48 48s48-21.5 48-48zM48 304c26.5 0 48-21.5 48-48s-21.5-48-48-48s-48 21.5-48 48s21.5 48 48 48zm464-48c0-26.5-21.5-48-48-48s-48 21.5-48 48s21.5 48 48 48s48-21.5 48-48zM142.9 437c18.7-18.7 18.7-49.1 0-67.9s-49.1-18.7-67.9 0s-18.7 49.1 0 67.9s49.1 18.7 67.9 0zm0-294.2c18.7-18.7 18.7-49.1 0-67.9S93.7 56.2 75 75s-18.7 49.1 0 67.9s49.1 18.7 67.9 0zM369.1 437c18.7 18.7 49.1 18.7 67.9 0s18.7-49.1 0-67.9s-49.1-18.7-67.9 0s-18.7 49.1 0 67.9z" / > < / svg > < / span >
< / div >
< / div >
< / form >
< div id = "mdbook-searchresults-outer" class = "searchresults-outer hidden" >
< div id = "mdbook-searchresults-header" class = "searchresults-header" > < / div >
< ul id = "mdbook-searchresults" >
< / ul >
< / div >
< / div >
<!-- Apply ARIA attributes after the sidebar and the sidebar toggle button are added to the DOM -->
< script >
document.getElementById('mdbook-sidebar-toggle').setAttribute('aria-expanded', sidebar === 'visible');
document.getElementById('mdbook-sidebar').setAttribute('aria-hidden', sidebar !== 'visible');
Array.from(document.querySelectorAll('#mdbook-sidebar a')).forEach(function(link) {
link.setAttribute('tabIndex', sidebar === 'visible' ? 0 : -1);
});
< / script >
< div id = "mdbook-content" class = "content" >
< main >
< h1 id = "使用-tracing-输出自定义的-rust-日志" > < a class = "header" href = "#使用-tracing-输出自定义的-rust-日志" > 使用 tracing 输出自定义的 Rust 日志< / a > < / h1 >
< p > 在 < a href = "https://docs.rs/crate/tracing/latest" > tracing< / a > 包出来前， < code > log< / code > 有一战之力，但是 < code > log< / code > 的功能相对来说还是简单一些。在大名鼎鼎的 tokio 开发团队推出 < code > tracing< / code > 后，我现在坚定的认为 < code > tracing< / code > 就是未来！< / p >
< blockquote >
< p > 截至目前， ， < a href = "https://github.com/tokio-rs/console" > console< / a > ！ < / p >
< / blockquote >
< p > 基于这种坚定的信仰，我们决定将公司之前使用的 < code > log< / code > 包替换成 < code > tracing< / code > ，但是有一个问题：后者提供的 JSON logger 总感觉不是那个味儿。这意味着，对于程序员来说，最快乐的时光又要到来了：定制自己的开发工具。< / p >
< p > 好了，闲话少说，下面我们一起来看看该如何构建自己的 logger， < / p >
< h2 id = "打地基1" > < a class = "header" href = "#打地基1" > 打地基(1)< / a > < / h2 >
< p > 首先，使用 < code > cargo new --bin test-tracing< / code > 创建一个新的二进制类型( binary )的项目。< / p >
< p > 然后引入以下依赖：< / p >
< pre > < code class = "language-toml" > # in cargo.toml
[dependencies]
serde_json = "1"
tracing = "0.1"
tracing-subscriber = "0.3"
< / code > < / pre >
< p > 其中 < code > tracing-subscriber< / code > 用于订阅正在发生的日志、监控事件，然后可以对它们进行进一步的处理。< code > serde_json< / code > 可以帮我们更好的处理格式化的 JSON， < / p >
< p > 下面来实现一个基本功能：设置自定义的 logger， < code > info!< / code > 来打印一行日志。< / p >
< pre class = "playground" > < code class = "language-rust edition2021" > // in examples/figure_0/main.rs
use tracing::info;
use tracing_subscriber::prelude::*;
mod custom_layer;
use custom_layer::CustomLayer;
fn main() {
// 设置 `tracing-subscriber` 对 tracing 数据的处理方式
tracing_subscriber::registry().with(CustomLayer).init();
// 打印一条简单的日志。用 `tracing` 的行话来说，`info!` 将创建一个事件
info!(a_bool = true, answer = 42, message = "first example");
}< / code > < / pre >
< p > 大家会发现，上面引入了一个模块 < code > custom_layer< / code > ， ， < code > tracing-subscriber< / code > 提供了一个特征 < a href = "https://docs.rs/tracing-subscriber/0.3/tracing_subscriber/layer/trait.Layer.html" > < code > Layer< / code > < / a > 专门用于处理 < code > tracing< / code > 的各种事件( span, event )。< / p >
< pre class = "playground" > < code class = "language-rust edition2021" > < span class = "boring" > #![allow(unused)]
< / span > < span class = "boring" > fn main() {
< / span > // in examples/figure_0/custom_layer.rs
use tracing_subscriber::Layer;
pub struct CustomLayer;
impl< S> Layer< S> for CustomLayer where S: tracing::Subscriber {}
< span class = "boring" > }< / span > < / code > < / pre >
< p > 由于还没有填入任何代码，运行该示例比你打的水漂还无力 - 毫无效果。< / p >
< h2 id = "捕获事件" > < a class = "header" href = "#捕获事件" > 捕获事件< / a > < / h2 >
< p > 在 < code > tracing< / code > 中，当 < code > info!< / code > 、< code > error!< / code > 等日志宏被调用时，就会产生一个相应的< a href = "https://docs.rs/tracing/0.1/tracing/event/struct.Event.html" > 事件 Event< / a > 。< / p >
< p > 而我们首先，就要为之前的 < code > Layer< / code > 特征实现 < code > on_event< / code > 方法。< / p >
< pre class = "playground" > < code class = "language-rust editable edition2021" > // in examples/figure_0/custom_layer.rs
where
S: tracing::Subscriber,
{
fn on_event(
& self,
event: & tracing::Event< '_> ,
_ctx: tracing_subscriber::layer::Context< '_, S> ,
) {
println!("Got event!");
println!(" level={:?}", event.metadata().level());
println!(" target={:?}", event.metadata().target());
println!(" name={:?}", event.metadata().name());
for field in event.fields() {
println!(" field={}", field.name());
}
}
}< / code > < / pre >
< p > 从代码中可以看出，我们打印了事件中包含的事件名、日志等级以及事件发生的代码路径。运行后，可以看到以下输出:< / p >
< pre > < code class = "language-properties" > $ cargo run --example figure_1
Got event!
level=Level(Info)
target="figure_1"
name="event examples/figure_1/main.rs:10"
field=a_bool
field=answer
field=message
< / code > < / pre >
< p > 但是奇怪的是，我们无法通过 API 来获取到具体的 < code > field< / code > 值。还有就是，上面的输出还不是 JSON 格式。< / p >
< p > 现在问题来了，要创建自己的 logger， < code > filed< / code > 显然是不靠谱的。< / p >
< h3 id = "访问者模式" > < a class = "header" href = "#访问者模式" > 访问者模式< / a > < / h3 >
< p > 在设计上，< code > tracing< / code > 作出了一个选择：永远不会自动存储产生的事件数据( spans, events )。如果我们要获取这些数据，就必须自己手动存储。< / p >
< p > 解决办法就是使用访问者模式(Visitor Pattern)：手动实现 < code > Visit< / code > 特征去获取事件中的值。< code > Visit< / code > 为每个 < code > tracing< / code > 可以处理的类型都提供了对应的 < code > record_X< / code > 方法。< / p >
< pre class = "playground" > < code class = "language-rust edition2021" > < span class = "boring" > #![allow(unused)]
< / span > < span class = "boring" > fn main() {
< / span > // in examples/figure_2/custom_layer.rs
struct PrintlnVisitor;
impl tracing::field::Visit for PrintlnVisitor {
fn record_f64(& mut self, field: & tracing::field::Field, value: f64) {
println!(" field={} value={}", field.name(), value)
}
fn record_i64(& mut self, field: & tracing::field::Field, value: i64) {
println!(" field={} value={}", field.name(), value)
}
fn record_u64(& mut self, field: & tracing::field::Field, value: u64) {
println!(" field={} value={}", field.name(), value)
}
fn record_bool(& mut self, field: & tracing::field::Field, value: bool) {
println!(" field={} value={}", field.name(), value)
}
fn record_str(& mut self, field: & tracing::field::Field, value: & str) {
println!(" field={} value={}", field.name(), value)
}
fn record_error(
& mut self,
field: & tracing::field::Field,
value: & (dyn std::error::Error + 'static),
) {
println!(" field={} value={}", field.name(), value)
}
fn record_debug(& mut self, field: & tracing::field::Field, value: & dyn std::fmt::Debug) {
println!(" field={} value={:?}", field.name(), value)
}
}
< span class = "boring" > }< / span > < / code > < / pre >
< p > 然后在之前的 < code > on_event< / code > 中来使用这个新的访问者： < code > event.record(& mut visitor)< / code > 可以访问其中的所有值。< / p >
< pre class = "playground" > < code class = "language-rust edition2021" > < span class = "boring" > #![allow(unused)]
< / span > < span class = "boring" > fn main() {
< / span > // in examples/figure_2/custom_layer.rs
fn on_event(
& self,
event: & tracing::Event< '_> ,
_ctx: tracing_subscriber::layer::Context< '_, S> ,
) {
println!("Got event!");
println!(" level={:?}", event.metadata().level());
println!(" target={:?}", event.metadata().target());
println!(" name={:?}", event.metadata().name());
let mut visitor = PrintlnVisitor;
event.record(& mut visitor);
}
< span class = "boring" > }< / span > < / code > < / pre >
< p > 这段代码看起来有模有样，来运行下试试：< / p >
< pre > < code class = "language-properties" > $ cargo run --example figure_2
Got event!
level=Level(Info)
target="figure_2"
name="event examples/figure_2/main.rs:10"
field=a_bool value=true
field=answer value=42
field=message value=first example
< / code > < / pre >
< p > Bingo ! 一切完美运行 ！ < / p >
< h3 id = "构建-json-logger" > < a class = "header" href = "#构建-json-logger" > 构建 JSON logger< / a > < / h3 >
< p > 目前为止，离我们想要的 JSON logger 只差一步了。下面来实现一个 < code > JsonVisitor< / code > 替代之前的 < code > PrintlnVisitor< / code > 用于构建一个 JSON 对象。< / p >
< pre class = "playground" > < code class = "language-rust edition2021" > < span class = "boring" > #![allow(unused)]
< / span > < span class = "boring" > fn main() {
< / span > // in examples/figure_3/custom_layer.rs
impl< 'a> tracing::field::Visit for JsonVisitor< 'a> {
fn record_f64(& mut self, field: & tracing::field::Field, value: f64) {
self.0
.insert(field.name().to_string(), serde_json::json!(value));
}
fn record_i64(& mut self, field: & tracing::field::Field, value: i64) {
self.0
.insert(field.name().to_string(), serde_json::json!(value));
}
fn record_u64(& mut self, field: & tracing::field::Field, value: u64) {
self.0
.insert(field.name().to_string(), serde_json::json!(value));
}
fn record_bool(& mut self, field: & tracing::field::Field, value: bool) {
self.0
.insert(field.name().to_string(), serde_json::json!(value));
}
fn record_str(& mut self, field: & tracing::field::Field, value: & str) {
self.0
.insert(field.name().to_string(), serde_json::json!(value));
}
fn record_error(
& mut self,
field: & tracing::field::Field,
value: & (dyn std::error::Error + 'static),
) {
self.0.insert(
field.name().to_string(),
serde_json::json!(value.to_string()),
);
}
fn record_debug(& mut self, field: & tracing::field::Field, value: & dyn std::fmt::Debug) {
self.0.insert(
field.name().to_string(),
serde_json::json!(format!("{:?}", value)),
);
}
}
< span class = "boring" > }< / span > < / code > < / pre >
< pre class = "playground" > < code class = "language-rust edition2021" > < span class = "boring" > #![allow(unused)]
< / span > < span class = "boring" > fn main() {
< / span > // in examples/figure_3/custom_layer.rs
fn on_event(
& self,
event: & tracing::Event< '_> ,
_ctx: tracing_subscriber::layer::Context< '_, S> ,
) {
// Covert the values into a JSON object
let mut fields = BTreeMap::new();
let mut visitor = JsonVisitor(& mut fields);
event.record(& mut visitor);
// Output the event in JSON
let output = serde_json::json!({
"target": event.metadata().target(),
"name": event.metadata().name(),
"level": format!("{:?}", event.metadata().level()),
"fields": fields,
});
println!("{}", serde_json::to_string_pretty(& output).unwrap());
}
< span class = "boring" > }< / span > < / code > < / pre >
< p > 继续运行:< / p >
< pre > < code class = "language-properties" > $ cargo run --example figure_3
{
"fields": {
"a_bool": true,
"answer": 42,
"message": "first example"
},
"level": "Level(Info)",
"name": "event examples/figure_3/main.rs:10",
"target": "figure_3"
}
< / code > < / pre >
< p > 终于，我们实现了自己的 logger， < code > Layer< / code > 就可以添加到 < code > tracing-subscriber< / code > 中用于记录日志事件。< / p >
< p > 下面再来一起看看如何使用< code > tracing< / code > 提供的 < code > period-of-time spans< / code > 为日志增加更详细的上下文信息。< / p >
< h3 id = "何为-span" > < a class = "header" href = "#何为-span" > 何为 span< / a > < / h3 >
< p > 在之前我们多次提到 span 这个词，但是何为 span？ < / p >
< p > 不知道大家知道分布式追踪不？在分布式系统中每一个请求从开始到返回，会经过多个服务，这条请求路径被称为请求跟踪链路( trace )，可以看出，一条链路是由多个部分组成，我们可以简单的把其中一个部分认为是一个 span。< / p >
< p > 跟 log 是对某个时间点的记录不同， ， ， ， < / p >
< p > 由此可见， < / p >
< p > 在理解后，再来看看该如何为自定义的 logger 实现 spans。< / p >
< h3 id = "打地基2" > < a class = "header" href = "#打地基2" > 打地基(2)< / a > < / h3 >
< p > 先来创建一个外部 span 和一个内部 span， ， < / p >
< ul >
< li > 进入外部 span
< ul >
< li > 进入内部 span
< ul >
< li > 事件已创建，内部 span 是它的父 span， < / li >
< / ul >
< / li >
< li > 结束内部 span< / li >
< / ul >
< / li >
< li > 结束外部 span< / li >
< / ul >
< blockquote >
< p > 有些同学可能还是不太理解，你就把 span 理解成为监控埋点，进入 span == 埋点开始，结束 span == 埋点结束< / p >
< / blockquote >
< p > 在下面的代码中，当使用 < code > span.enter()< / code > 创建的 span 超出作用域时，将自动退出：根据 < code > Drop< / code > 特征触发的顺序，< code > inner_span< / code > 将先退出，然后才是 < code > outer_span< / code > 的退出。< / p >
< pre class = "playground" > < code class = "language-rust edition2021" > // in examples/figure_5/main.rs
use tracing::{debug_span, info, info_span};
use tracing_subscriber::prelude::*;
mod custom_layer;
use custom_layer::CustomLayer;
fn main() {
tracing_subscriber::registry().with(CustomLayer).init();
let outer_span = info_span!("outer", level = 0);
let _outer_entered = outer_span.enter();
let inner_span = debug_span!("inner", level = 1);
let _inner_entered = inner_span.enter();
info!(a_bool = true, answer = 42, message = "first example");
}< / code > < / pre >
< p > 再回到事件处理部分，通过使用 < code > examples/figure_0/main.rs< / code > 我们能获取到事件的父 span， ， ， < code > ctx.event_scope(event)< / code > 来迭代所有 span 会更加简单好用。< / p >
< p > 注意，这种迭代顺序类似于栈结构，以上面的代码为例，先被迭代的是 < code > inner_span< / code > ，然后才是 < code > outer_span< / code > 。< / p >
< p > 当然，如果你不想以类似于出栈的方式访问，还可以使用 < code > scope.from_root()< / code > 直接反转，此时的访问将从最外层开始： < code > outer -> innter< / code > 。< / p >
< p > 对了，为了使用 < code > ctx.event_scope()< / code > ，我们的订阅者还需实现 < code > LookupRef< / code > 。提前给出免责声明：这里的实现方式有些诡异，大家可能难以理解，但是..我们其实也无需理解，只要这么用即可。< / p >
< blockquote >
< p > 译者注：这里用到了高阶生命周期 HRTB( Higher Ranke Trait Bounds ) 的概念，一般的读者无需了解，感兴趣的可以看看(这里)[https://doc.rust-lang.org/nomicon/hrtb.html]< / p >
< / blockquote >
< pre class = "playground" > < code class = "language-rust edition2021" > < span class = "boring" > #![allow(unused)]
< / span > < span class = "boring" > fn main() {
< / span > // in examples/figure_5/custom_layer.rs
impl< S> Layer< S> for CustomLayer
where
S: tracing::Subscriber,
// 好可怕! 还好我们不需要理解它，只要使用即可
S: for< 'lookup> tracing_subscriber::registry::LookupSpan< 'lookup> ,
{
fn on_event(& self, event: & tracing::Event< '_> , ctx: tracing_subscriber::layer::Context< '_, S> ) {
// 父 span
let parent_span = ctx.event_span(event).unwrap();
println!("parent span");
println!(" name={}", parent_span.name());
println!(" target={}", parent_span.metadata().target());
println!();
// 迭代范围内的所有的 spans
let scope = ctx.event_scope(event).unwrap();
for span in scope.from_root() {
println!("an ancestor span");
println!(" name={}", span.name());
println!(" target={}", span.metadata().target());
}
}
}
< span class = "boring" > }< / span > < / code > < / pre >
< p > 运行下看看效果:< / p >
< pre > < code class = "language-properties" > $ cargo run --example figure_5
parent span
name=inner
target=figure_5
an ancestor span
name=outer
target=figure_5
an ancestor span
name=inner
target=figure_5
< / code > < / pre >
< p > 细心的同学可能会发现，这里怎么也没有 field 数据？没错，而且恰恰是这些 field 包含的数据才让日志和监控有意义。那我们可以像之前一样，使用访问器 Visitor 来解决吗？< / p >
< h3 id = "span-的数据在哪里" > < a class = "header" href = "#span-的数据在哪里" > span 的数据在哪里< / a > < / h3 >
< p > 答案是： < code > ctx.event_scope < / code > 返回的东东没有任何办法可以访问其中的字段。< / p >
< p > 不知道大家还记得我们为何之前要使用访问器吗？很简单，因为 < code > tracing< / code > 默认不会去存储数据，既然如此，那 < code > span< / code > 这种跨了某个时间段的，就更不可能去存储数据了。< / p >
< p > 现在只能看看 < code > Layer< / code > 特征有没有提供其它的方法了，哦呦，发现了一个 < code > on_new_span< / code > ，从名字可以看出，该方法是在 < code > span< / code > 创建时调用的。< / p >
< pre class = "playground" > < code class = "language-rust edition2021" > < span class = "boring" > #![allow(unused)]
< / span > < span class = "boring" > fn main() {
< / span > // in examples/figure_6/custom_layer.rs
impl< S> Layer< S> for CustomLayer
where
S: tracing::Subscriber,
S: for< 'lookup> tracing_subscriber::registry::LookupSpan< 'lookup> ,
{
fn on_new_span(
& self,
attrs: & tracing::span::Attributes< '_> ,
id: & tracing::span::Id,
ctx: tracing_subscriber::layer::Context< '_, S> ,
) {
let span = ctx.span(id).unwrap();
println!("Got on_new_span!");
println!(" level={:?}", span.metadata().level());
println!(" target={:?}", span.metadata().target());
println!(" name={:?}", span.metadata().name());
// Our old friend, `println!` exploration.
let mut visitor = PrintlnVisitor;
attrs.record(& mut visitor);
}
}
< span class = "boring" > }< / span > < / code > < / pre >
< pre > < code class = "language-properties" > $ cargo run --example figure_6
Got on_new_span!
level=Level(Info)
target="figure_7"
name="outer"
field=level value=0
Got on_new_span!
level=Level(Debug)
target="figure_7"
name="inner"
field=level value=1
< / code > < / pre >
< p > 芜湖! 我们的数据回来了！但是这里有一个隐患：只能在创建的时候去访问数据。如果仅仅是为了记录 spans， ， < / p >
< p > 如果 < code > tracing< / code > 不能存储数据，那我们这些可怜的开发者该怎么办？< / p >
< h3 id = "自己存储-span-数据" > < a class = "header" href = "#自己存储-span-数据" > 自己存储 span 数据< / a > < / h3 >
< p > 何为一个优秀的程序员？能偷懒的时候绝不多动半跟手指，但是需要勤快的时候，也是自己动手丰衣足食的典型。< / p >
< p > 因此，既然 < code > tracing< / code > 不支持，那就自己实现吧。先确定一个目标：捕获 span 的数据，然后存储在某个地方以便后续访问。< / p >
< p > 好在 < code > tracing-subscriber< / code > 提供了扩展 extensions 的方式，可以让我们轻松地存储自己的数据，该扩展甚至可以跟每一个 span 联系在一起！< / p >
< p > 虽然我们可以把之前见过的 < code > BTreeMap< String, serde_json::Value> < / code > 存在扩展中，但是由于扩展数据是被 registry 中的所有layers 所共享的，因此出于私密性的考虑，还是只保存私有字段比较合适。这里使用一个 newtype 模式来创建新的类型:< / p >
< pre class = "playground" > < code class = "language-rust edition2021" > < span class = "boring" > #![allow(unused)]
< / span > < span class = "boring" > fn main() {
< / span > // in examples/figure_8/custom_layer.rs
#[derive(Debug)]
struct CustomFieldStorage(BTreeMap< String, serde_json::Value> );
< span class = "boring" > }< / span > < / code > < / pre >
< p > 每次发现一个新的 span 时，都基于它来构建一个 JSON 对象，然后将其存储在扩展数据中。< / p >
< pre class = "playground" > < code class = "language-rust edition2021" > < span class = "boring" > #![allow(unused)]
< / span > < span class = "boring" > fn main() {
< / span > // in examples/figure_8/custom_layer.rs
fn on_new_span(
& self,
attrs: & tracing::span::Attributes< '_> ,
id: & tracing::span::Id,
ctx: tracing_subscriber::layer::Context< '_, S> ,
) {
// 基于 field 值来构建我们自己的 JSON 对象
let mut fields = BTreeMap::new();
let mut visitor = JsonVisitor(& mut fields);
attrs.record(& mut visitor);
// 使用之前创建的 newtype 包裹下
let storage = CustomFieldStorage(fields);
// 获取内部 span 数据的引用
let span = ctx.span(id).unwrap();
// 获取扩展，用于存储我们的 span 数据
let mut extensions = span.extensions_mut();
// 存储！
extensions.insert::< CustomFieldStorage> (storage);
}
< span class = "boring" > }< / span > < / code > < / pre >
< p > 这样，未来任何时候我们都可以取到该 span 包含的数据( 例如在 < code > on_event< / code > 方法中 )。< / p >
< pre class = "playground" > < code class = "language-rust edition2021" > < span class = "boring" > #![allow(unused)]
< / span > < span class = "boring" > fn main() {
< / span > // in examples/figure_8/custom_layer.rs
fn on_event(& self, event: & tracing::Event< '_> , ctx: tracing_subscriber::layer::Context< '_, S> ) {
let scope = ctx.event_scope(event).unwrap();
println!("Got event!");
for span in scope.from_root() {
let extensions = span.extensions();
let storage = extensions.get::< CustomFieldStorage> ().unwrap();
println!(" span");
println!(" target={:?}", span.metadata().target());
println!(" name={:?}", span.metadata().name());
println!(" stored fields={:?}", storage);
}
}
< span class = "boring" > }< / span > < / code > < / pre >
< h3 id = "功能齐全的-json-logger" > < a class = "header" href = "#功能齐全的-json-logger" > 功能齐全的 JSON logger< / a > < / h3 >
< p > 截至目前，我们已经学了不少东西，下面来利用这些知识实现最后的 JSON logger。< / p >
< pre class = "playground" > < code class = "language-rust edition2021" > < span class = "boring" > #![allow(unused)]
< / span > < span class = "boring" > fn main() {
< / span > // in examples/figure_9/custom_layer.rs
fn on_event(& self, event: & tracing::Event< '_> , ctx: tracing_subscriber::layer::Context< '_, S> ) {
// All of the span context
let scope = ctx.event_scope(event).unwrap();
let mut spans = vec![];
for span in scope.from_root() {
let extensions = span.extensions();
let storage = extensions.get::< CustomFieldStorage> ().unwrap();
let field_data: & BTreeMap< String, serde_json::Value> = & storage.0;
spans.push(serde_json::json!({
"target": span.metadata().target(),
"name": span.name(),
"level": format!("{:?}", span.metadata().level()),
"fields": field_data,
}));
}
// The fields of the event
let mut fields = BTreeMap::new();
let mut visitor = JsonVisitor(& mut fields);
event.record(& mut visitor);
// And create our output
let output = serde_json::json!({
"target": event.metadata().target(),
"name": event.metadata().name(),
"level": format!("{:?}", event.metadata().level()),
"fields": fields,
"spans": spans,
});
println!("{}", serde_json::to_string_pretty(& output).unwrap());
}
< span class = "boring" > }< / span > < / code > < / pre >
< pre > < code class = "language-properties" > $ cargo run --example figure_9
{
"fields": {
"a_bool": true,
"answer": 42,
"message": "first example"
},
"level": "Level(Info)",
"name": "event examples/figure_9/main.rs:16",
"spans": [
{
"fields": {
"level": 0
},
"level": "Level(Info)",
"name": "outer",
"target": "figure_9"
},
{
"fields": {
"level": 1
},
"level": "Level(Debug)",
"name": "inner",
"target": "figure_9"
}
],
"target": "figure_9"
}
< / code > < / pre >
< p > 嗯，完美。< / p >
< h3 id = "等等你说功能齐全" > < a class = "header" href = "#等等你说功能齐全" > 等等，你说功能齐全？< / a > < / h3 >
< p > 上面的代码在发布到生产环境后，依然运行地相当不错，但是我发现还缺失了一个功能: span 在创建之后，依然要能记录数据。< / p >
< pre class = "playground" > < code class = "language-rust edition2021" > < span class = "boring" > #![allow(unused)]
< / span > < span class = "boring" > fn main() {
< / span > // in examples/figure_10/main.rs
let outer_span = info_span!("outer", level = 0, other_field = tracing::field::Empty);
let _outer_entered = outer_span.enter();
// Some code...
outer_span.record("other_field", & 7);
< span class = "boring" > }< / span > < / code > < / pre >
< p > 如果基于之前的代码运行上面的代码，我们将不会记录 < code > other_field< / code > ，因为该字段在收到 < code > on_new_span< / code > 事件时，还不存在。< / p >
< p > 对此，< code > Layer< / code > 提供了 < code > on_record< / code > 方法：< / p >
< pre class = "playground" > < code class = "language-rust edition2021" > < span class = "boring" > #![allow(unused)]
< / span > < span class = "boring" > fn main() {
< / span > // in examples/figure_10/custom_layer.rs
fn on_record(
& self,
id: & tracing::span::Id,
values: & tracing::span::Record< '_> ,
ctx: tracing_subscriber::layer::Context< '_, S> ,
) {
// 获取正在记录数据的 span
let span = ctx.span(id).unwrap();
// 获取数据的可变引用，该数据是在 on_new_span 中创建的
let mut extensions_mut = span.extensions_mut();
let custom_field_storage: & mut CustomFieldStorage =
extensions_mut.get_mut::< CustomFieldStorage> ().unwrap();
let json_data: & mut BTreeMap< String, serde_json::Value> = & mut custom_field_storage.0;
// 使用我们的访问器老朋友
let mut visitor = JsonVisitor(json_data);
values.record(& mut visitor);
}
< span class = "boring" > }< / span > < / code > < / pre >
< p > 终于，在最后，我们拥有了一个功能齐全的自定义的 JSON logger， ， ， < / p >
< blockquote >
< p > 在以下 github 仓库，可以找到完整的代码: https://github.com/bryanburgers/tracing-blog-post< / p >
< p > 本文由 Rustt 提供翻译
原文链接: https://github.com/studyrs/Rustt/blob/main/Articles/%5B2022-04-07%5D%20在%20Rust%20中使用%20tracing%20自定义日志.md< / p >
< / blockquote >
< / main >
< nav class = "nav-wrapper" aria-label = "Page navigation" >
<!-- Mobile navigation buttons -->
< a rel = "prev" href = "../logs/tracing.html" class = "mobile-nav-chapters previous" title = "Previous chapter" aria-label = "Previous chapter" aria-keyshortcuts = "Left" >
< span class = fa-svg > < svg xmlns = "http://www.w3.org/2000/svg" viewBox = "0 0 320 512" > <!-- ! Font Awesome Free 6.2.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2022 Fonticons, Inc. --> < path d = "M41.4 233.4c-12.5 12.5-12.5 32.8 0 45.3l160 160c12.5 12.5 32.8 12.5 45.3 0s12.5-32.8 0-45.3L109.3 256 246.6 118.6c12.5-12.5 12.5-32.8 0-45.3s-32.8-12.5-45.3 0l-160 160z" / > < / svg > < / span >
< / a >
< a rel = "next prefetch" href = "../logs/observe/intro.html" class = "mobile-nav-chapters next" title = "Next chapter" aria-label = "Next chapter" aria-keyshortcuts = "Right" >
< span class = fa-svg > < svg xmlns = "http://www.w3.org/2000/svg" viewBox = "0 0 320 512" > <!-- ! Font Awesome Free 6.2.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2022 Fonticons, Inc. --> < path d = "M278.6 233.4c12.5 12.5 12.5 32.8 0 45.3l-160 160c-12.5 12.5-32.8 12.5-45.3 0s-12.5-32.8 0-45.3L210.7 256 73.4 118.6c-12.5-12.5-12.5-32.8 0-45.3s32.8-12.5 45.3 0l160 160z" / > < / svg > < / span >
< / a >
< div style = "clear: both" > < / div >
< / nav >
< / div >
< / div >
< nav class = "nav-wide-wrapper" aria-label = "Page navigation" >
< a rel = "prev" href = "../logs/tracing.html" class = "nav-chapters previous" title = "Previous chapter" aria-label = "Previous chapter" aria-keyshortcuts = "Left" >
< span class = fa-svg > < svg xmlns = "http://www.w3.org/2000/svg" viewBox = "0 0 320 512" > <!-- ! Font Awesome Free 6.2.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2022 Fonticons, Inc. --> < path d = "M41.4 233.4c-12.5 12.5-12.5 32.8 0 45.3l160 160c12.5 12.5 32.8 12.5 45.3 0s12.5-32.8 0-45.3L109.3 256 246.6 118.6c12.5-12.5 12.5-32.8 0-45.3s-32.8-12.5-45.3 0l-160 160z" / > < / svg > < / span >
< / a >
< a rel = "next prefetch" href = "../logs/observe/intro.html" class = "nav-chapters next" title = "Next chapter" aria-label = "Next chapter" aria-keyshortcuts = "Right" >
< span class = fa-svg > < svg xmlns = "http://www.w3.org/2000/svg" viewBox = "0 0 320 512" > <!-- ! Font Awesome Free 6.2.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2022 Fonticons, Inc. --> < path d = "M278.6 233.4c12.5 12.5 12.5 32.8 0 45.3l-160 160c-12.5 12.5-32.8 12.5-45.3 0s-12.5-32.8 0-45.3L210.7 256 73.4 118.6c-12.5-12.5-12.5-32.8 0-45.3s32.8-12.5 45.3 0l160 160z" / > < / svg > < / span >
< / a >
< / nav >
< / div >
< template id = fa-eye > < span class = fa-svg > < svg xmlns = "http://www.w3.org/2000/svg" viewBox = "0 0 576 512" > <!-- ! Font Awesome Free 6.2.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2022 Fonticons, Inc. --> < path d = "M288 32c-80.8 0-145.5 36.8-192.6 80.6C48.6 156 17.3 208 2.5 243.7c-3.3 7.9-3.3 16.7 0 24.6C17.3 304 48.6 356 95.4 399.4C142.5 443.2 207.2 480 288 480s145.5-36.8 192.6-80.6c46.8-43.5 78.1-95.4 93-131.1c3.3-7.9 3.3-16.7 0-24.6c-14.9-35.7-46.2-87.7-93-131.1C433.5 68.8 368.8 32 288 32zM432 256c0 79.5-64.5 144-144 144s-144-64.5-144-144s64.5-144 144-144s144 64.5 144 144zM288 192c0 35.3-28.7 64-64 64c-11.5 0-22.3-3-31.6-8.4c-.2 2.8-.4 5.5-.4 8.4c0 53 43 96 96 96s96-43 96-96s-43-96-96-96c-2.8 0-5.6 .1-8.4 .4c5.3 9.3 8.4 20.1 8.4 31.6z" / > < / svg > < / span > < / template >
< template id = fa-eye-slash > < span class = fa-svg > < svg xmlns = "http://www.w3.org/2000/svg" viewBox = "0 0 640 512" > <!-- ! Font Awesome Free 6.2.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2022 Fonticons, Inc. --> < path d = "M38.8 5.1C28.4-3.1 13.3-1.2 5.1 9.2S-1.2 34.7 9.2 42.9l592 464c10.4 8.2 25.5 6.3 33.7-4.1s6.3-25.5-4.1-33.7L525.6 386.7c39.6-40.6 66.4-86.1 79.9-118.4c3.3-7.9 3.3-16.7 0-24.6c-14.9-35.7-46.2-87.7-93-131.1C465.5 68.8 400.8 32 320 32c-68.2 0-125 26.3-169.3 60.8L38.8 5.1zM223.1 149.5C248.6 126.2 282.7 112 320 112c79.5 0 144 64.5 144 144c0 24.9-6.3 48.3-17.4 68.7L408 294.5c5.2-11.8 8-24.8 8-38.5c0-53-43-96-96-96c-2.8 0-5.6 .1-8.4 .4c5.3 9.3 8.4 20.1 8.4 31.6c0 10.2-2.4 19.8-6.6 28.3l-90.3-70.8zm223.1 298L373 389.9c-16.4 6.5-34.3 10.1-53 10.1c-79.5 0-144-64.5-144-144c0-6.9 .5-13.6 1.4-20.2L83.1 161.5C60.3 191.2 44 220.8 34.5 243.7c-3.3 7.9-3.3 16.7 0 24.6c14.9 35.7 46.2 87.7 93 131.1C174.5 443.2 239.2 480 320 480c47.8 0 89.9-12.9 126.2-32.5z" / > < / svg > < / span > < / template >
< template id = fa-copy > < span class = fa-svg > < svg xmlns = "http://www.w3.org/2000/svg" viewBox = "0 0 512 512" > <!-- ! Font Awesome Free 6.2.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2022 Fonticons, Inc. --> < path d = "M502.6 70.63l-61.25-61.25C435.4 3.371 427.2 0 418.7 0H255.1c-35.35 0-64 28.66-64 64l.0195 256C192 355.4 220.7 384 256 384h192c35.2 0 64-28.8 64-64V93.25C512 84.77 508.6 76.63 502.6 70.63zM464 320c0 8.836-7.164 16-16 16H255.1c-8.838 0-16-7.164-16-16L239.1 64.13c0-8.836 7.164-16 16-16h128L384 96c0 17.67 14.33 32 32 32h47.1V320zM272 448c0 8.836-7.164 16-16 16H63.1c-8.838 0-16-7.164-16-16L47.98 192.1c0-8.836 7.164-16 16-16H160V128H63.99c-35.35 0-64 28.65-64 64l.0098 256C.002 483.3 28.66 512 64 512h192c35.2 0 64-28.8 64-64v-32h-47.1L272 448z" / > < / svg > < / span > < / template >
< template id = fa-play > < span class = fa-svg > < svg xmlns = "http://www.w3.org/2000/svg" viewBox = "0 0 384 512" > <!-- ! Font Awesome Free 6.2.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2022 Fonticons, Inc. --> < path d = "M73 39c-14.8-9.1-33.4-9.4-48.5-.9S0 62.6 0 80V432c0 17.4 9.4 33.4 24.5 41.9s33.7 8.1 48.5-.9L361 297c14.3-8.7 23-24.2 23-41s-8.7-32.2-23-41L73 39z" / > < / svg > < / span > < / template >
< template id = fa-clock-rotate-left > < span class = fa-svg > < svg xmlns = "http://www.w3.org/2000/svg" viewBox = "0 0 512 512" > <!-- ! Font Awesome Free 6.2.0 by @fontawesome - https://fontawesome.com License - https://fontawesome.com/license/free (Icons: CC BY 4.0, Fonts: SIL OFL 1.1, Code: MIT License) Copyright 2022 Fonticons, Inc. --> < path d = "M75 75L41 41C25.9 25.9 0 36.6 0 57.9V168c0 13.3 10.7 24 24 24H134.1c21.4 0 32.1-25.9 17-41l-30.8-30.8C155 85.5 203 64 256 64c106 0 192 86 192 192s-86 192-192 192c-40.8 0-78.6-12.7-109.7-34.4c-14.5-10.1-34.4-6.6-44.6 7.9s-6.6 34.4 7.9 44.6C151.2 495 201.7 512 256 512c141.4 0 256-114.6 256-256S397.4 0 256 0C185.3 0 121.3 28.7 75 75zm181 53c-13.3 0-24 10.7-24 24V256c0 6.4 2.5 12.5 7 17l72 72c9.4 9.4 24.6 9.4 33.9 0s9.4-24.6 0-33.9l-65-65V152c0-13.3-10.7-24-24-24z" / > < / svg > < / span > < / template >
< script >
window.playground_copyable = true;
< / script >
< script src = "../ace-2a3cd908.js" > < / script >
< script src = "../mode-rust-2c9d5c9a.js" > < / script >
< script src = "../editor-16ca416c.js" > < / script >
< script src = "../theme-dawn-4493f9c8.js" > < / script >
< script src = "../theme-tomorrow_night-9dbe62a9.js" > < / script >
< script src = "../elasticlunr-ef4e11c1.min.js" > < / script >
< script src = "../mark-09e88c2c.min.js" > < / script >
< script src = "../searcher-c2a407aa.js" > < / script >
< script src = "../clipboard-1626706a.min.js" > < / script >
< script src = "../highlight-abc7f01d.js" > < / script >
< script src = "../book-a0b12cfe.js" > < / script >
<!-- Custom JS scripts -->
< script src = "../assets/custom-7d8ae1df.js" > < / script >
< script src = "../assets/bigPicture-be03f9c8.js" > < / script >
< / div >
< / body >
< / html >
